All Automatic Microwave Frequency Counter Test System to GHz

by Larry L. Koepke

Testing the 5343A Microwave Frequency Counter, trie 5355A Automatic Frequency Converter and the 5356A.B.'C Frequency Converter Heads for conformity to alt ot their specifications over their entire frequency ranges is not a trivial task To handle this formidable job a special automatic test system had to be devised Some of its features are

1 The software programs are structured to allow the operator to run a full set ot tests automatically (without operator assistance), to select a single test to run, or to select frequencies and power levels manually (see Fig. 1)

Special Function Keys

Set and Read Status of5355A

Pre scaler

CW Sansltlllvy and Accuracy

Special Function Keys

Set and Read Status of5355A

Pre scaler

CW Sansltlllvy and Accuracy

Test 1

Test 5

Pretest«

Pulse Sensitivity

Presea let

Pulse Accuracy

RF Heed CW S«r>»Mvlty and Accuracy

RF Head

Pulse Sensitivity

Test 6

Pretest«

Pulse Sensitivity

Presea let

Pulse Accuracy

RF Heed CW S«r>»Mvlty and Accuracy

RF Head

Pulse Sensitivity

RF Head

Pulse Accuracy

Test 1

Test 5

Test 6

Tesl 7

RF Head

Pulse Accuracy

Fig, 1. Test program structure and spec/a/ function key assignments in the Microwave Counter Test System

2 The system can make numerous repetitive frequency measurements at different power levels automatically, freeing the test technician to aiign and/or repair instruments that have failed the automatic tests

3 The system provides failure reports to help the test technician locate instrument failures.

4 In the data log mode the system provides a printout of the complete test

5. The operalor is made aware of a failure or the end of a tes! by an audible signal

The Microwave Counter Test System is controlled by an HP 9825A Desktop Computer using HP-iB* signal sources (HP 3330B, HP8660C. HP 8672A) to derive the frequencies of 10 Hz to 40 GHz Frequencies of 18.5 GHz to 26.5 GHz are derived by doubling the 8672A frequencies of 9.25 GHz to 13 25 GHz Frequencies of 26 5 GHz to 40 GHz are derived by quadrupling the 8672A frequences of 6.625 GHz to 10 GHz

The system is capable of supplying CW or pulsed RF to the instruments under test. A 5359A Time Synthesizer is used to generate pulses to modulate the CW signal generator outputs HP 33311B/C Coaxial Switches used for signal switching and an HP 8495K 10-dB Step Attenuator are controlled via the HP-IB by three HP 59306A Relay Actuators. Two HP 436A Power Meters controlled via the HP-IB and one HP 432C Power Meter controlled via an HP 98032A 16-bit I/O Interface make the required power measurements Frequency measurements on the combined 5355A Converter (listen only) and 5356A/B/C Heads are made by the5345A Counter and output via the HP-IB to the 9825A Desktop Computer 5343A Microwave Frequency Counter frequency measurements are output directly via the HP-IB to the 9825A A separate HP 98034A HP-IB I/O interface was used for

"CompanLile with IEEE 488-197B.

the instruments under test (5343A or 5355A), so that an HP-IB failure in one of these instruments would not affect the system instruments under HP-IB control, which are on another 98034A HP-iB I/O Interface Fig. 2 is the system block diagram

The instrument test programs, associated data files, and special function keys are stored on the HP 9885M Flexible Disc When the system is first powered up the 9825A Computer automancaily loads track 0, file 0. the Start program loads the special function keys from the flexible disc and displays press s? kev for desired unf The operator presses the special function key on the 9825A corresponding to the instrument being tested, and the instrument test program selected by the operator is loaded trom the 9885M Flexible Disc nto the 9825A memory and executed from line 0 The operator now answers questions asked by the 9825A do you wish to data log17 yes or no: if yes enter the date, enter the instrument serial number The complete test is then executed

Larry L. Koepke

Larry Koepke has been a test and electrons tooling technician with HP since 1959 Born in Rockford, Iowa, he _ learned his electronics in the U.S. Army He assembled the test system and - i^™ wrote the test programs for the 5355A Frequency Converter. ;he 53S6A/B/S Heads, and the 5343A Microwave Counter A resident oi San Jose. California. Larry is married, has two daughters and one grandson and ikes to tide horses and bicycles.

^ Dnnhifli

Directional

LÜ1

w

Coupler

26.5 to

Frequency Synthesizer 2-18 GHz

Pulse Generator

Desktop Computer

Frequency Synthesizer 2-18 GHz

Pulse Generator

Desktop Computer

Frequency Synthesizer 12 MHz - 2 GHz

Frequency Synthesizer 10 Hz - 12 MHz

I/O Expa niter

Frequency Synthesizer 12 MHz - 2 GHz

Frequency Synthesizer 10 Hz - 12 MHz

I/O Expa niter

Thermistor

and Power

Meter

A

Unit Under

Test

A

Ftg. 2. Block diagram of the Microwave Counter Test System.

1 MHz

+

20 ns 100 ns t fis 10 /iS 100 fiS External Gate Width

1 ms

10 ms

Fig. 10. Gate error and resolution of frequency average measurements as a function of gate width portional lo external gate width. The calibration routine improves the accuracy about one order of magnitude. The residual gate error, shown in Fig. 10. is independent of gate time and may be decreased to 3 kHz for external gate widths from about 4/as to 100/^s. Since the resolution of the calibration factor is not zero and secondary 5345A main gale errors are present, 3 kHz is ihe accuracy limit. However, calibration is not used for external gate widths greater than 100/iS, so the accuracy is the same as the 5345A Counter in this region.

Since no pulse burst standard exists, pulse accuracy measurements are made with a CW source with the mainframe counter externally gated. Actual pulse measurements using the lest equipment described on page 11 typically are more accurate than the specification. Fig. 1 i shows the resulis of typical pulse measurements on an Ifl-GHz synthesizer as a function of pulse width.

Pulse modulation of a source causes phase modulation of the carrier, especially during the rise and fall times of the pulse. This can be a result of direct FM or 8»M, AM-to-FM conversion, or frequency pulling of the source. A video signal [feedthrough of the pulse modulation] may also be present along wit!: the modulated carrier, further distorting the waveshape. Although the 5355A's adaptive gate generator removes about 15 ns from the leading and trailing edges of the pulse, some phase modulation may remain, especially for short pulses. Therefore, frequency accuracy for burst measurements depends on input signal purity; any phase perturbations that cannot be removed by the 5355A will cause errors,

A typical CW statistical measurement ol a synthesized 18-GHz source with the source and counter time bases tied together using a 1-s gate time had a standard deviation (one sigma) of 0.57 Hz and a mean difference ol 0.08 Hz for 1000 measurements.

Self Check

The 5355A can perform six measurements, two using the prescaler input and four using the RF head input. With the prescaler, either pulse or CW mode can be selected. With the RF head, pulse auto, CW auto, pulse manual, or CW manual can be selected.

The 6000 microprocessor executes these complex algorithms using 12K bytes of ROM and IK bytes of RAM. With the flexibility the microprocessor allows, it was easy to implement special self-check routines that execute whenever the instrument is turned on. In the 5355A, the two RAM integrated circuits are verified for data-pattern read/Write and addressability. Then the two ROM integrated circuits are tested via a checksum. Following RAM and ROM tests, the synthesizer is programmed to three known frequencies and performs three 100-;« measur-ments to verify each setting. Should any of these power-on tests fail, the operator gets a unique ten-second warning display per failure. Thereafter, the 5355A will attempt to follow the measurement algorithm specified by the user.

Acknowledgments

The team that developed the 5355A and the 5356A'B/C was as follows: I.uiz Peregrino did most of the initial investigation. systems analysis, and synthesizer design. The MPU/HP-IB hardware was developed by John Shing. Mohamed Sayed was responsible for the 5356A/B/C heads He developed the 40-GHz sampler, VCO, sampler driver, high-pass filter, and power amplifier hybrids, and provided the integration and testing of the heads. The prescaler channel was the responsibility of Hans Jekat, who also designed the IF amplifiers and provided many solutions to systems problems. The mechanical designer of the 5355A was Dick Goo, and of the 5356A/B/C was Keith Leslie, Tool design was by Jerry Curran. Martin Neil provided the initial

10 MHz

100 kHz o fi

10 Hz

Specified Accuracy

Typical Measurements

Gate Time Gate Time

20 ns 100 ns 1 ps 10 ¿cs 100 jjS 1 ms 10 ms External Gate Width

Fig. 11. Typical measurements on an 18-GHz pulsed dilutee Peak pulse power is ■ JO dBm Each point is the average of 100 measurements.

marketing introduction, and Larry Johnson completed that assignment. Randy Goodner was the service engineer, and Larry Koepke built the microwave counter test system and wrote the software. Quality assurance was under the surveillance of foe Bourdet. Alex Campista and Ron Hartter were the pilot run technicians, lan Band was the lab engineering manager and Roger Smith the microwave counter section head. Many thanks to all of the people above and to all of the others that contributed to the production of these instruments.

References

1. J.L. Sot den, "A New Generation in Frequency and Time Measurement," Hewlett-Packard Journal, (une 1974,

2. A. Bologlu and V.A. Barber, " Microprocessor-Control led Harmonic Heterodyne Microwave Counter also Measures Amplitudes," Hewlett-Packard Journal, May 1978.

3. S.I. Gass, "Linear Programming, Methods and Applications," McGraw-Hill, 1964.

4. L. Peregrino, "A Technique that !s Insensitive to FM for Determining Harmonic Number and Sideband," Hewlett-Packard Journal. May 1978.

5. D,C, Chu, "Time Interval Averaging; Theory, Problems, and Solutions," Hewlett-Packard Journal, June 1974,

Richard F. Schneider

Dick Schneider is pro|ect manager for the 5355A Frequency Converter and the 5356A'B Frequency Converter Heads. With HP since 1964. he's contributed to the design of the 5240A, 5260A, and 5257A counter products, developed several microwave counter and phase-lock systems, and served as project manager for the 5340A Counter A native of Cleveland. Ohio, he graduated from Case Institute of Technology with a BSEE degree in 1952 , and spent several years designing mis-■1\ sile and satellite test equipment, mi-1 P crowave amplifiers, and telemetering, radar, and receiving systems before joining HP He also served in the U.S Coast Guard as a Loran specialist. Dick Is a member of IEEE and holds an MSEE degree from California State University at San Jose, received in 1968 He's married, has two sons, and relaxes with tennis and woodworking.

Robert W. Oftermann

Bob Offermann received his 8S degree in electrical engineering from California Institute of Technology in 1971, and for the next two years combined circuit design work at the U.S. Naval Undersea R&D Center with graduate studies at Caltech He received his MS degree in ■ [¡fjji v * 1973 and joined HP shortly thereafter Bob has contributed to the design of the 5363A Time Interval Probes, done investigations on time interval measurements, designed the IF and gating circuits for the 5355A Frequency Con. ' Wfflj A f veher, ar|d served as the first 5355A production engmeer. A native of Stockton, California, he now lives in Saratoga, California. He's married and enjoys swimming, sailing, ballroom dancing, and theater

Ronald E. Felsenstein

It With HP since 1969, Ron Felsenstein Wi designed the processor for the 5345A i Counter, served for a year as a laser and logic production engineer, and was responsible for the 6800 lirmware and the digital interface design for the 5355A Frequency Converter. Born in Montevideo, Uruguay, he received his SB degree in electrical engineering _ from Massachusetts Institute of Technology in 1969. Now a resident of Santa Clara, California. Ron and his . family (he's married and has two children) enjoy winter camping In their recently acquired motorhome. Ron collects U.S. stamps and coins and is a dedicated do-it-yourselfer when it comes to car and home repairs.

40-GHz Frequency Converter Heads by Mohamed M. Sayed

THERE IS AN UPPER LIMIT to the frequencies at which automatic microwave frequency measurements may be made simply by connecting a coaxial cable between the source and the counter. This is because the cable's losses are generally greater for higher frequencies, thus demanding more sensitivity from the counter, wrhile microwave counters become less and less sensitive at higher frequencies. Thus a frequency is reached where not

Fig, 1. Model 5356A BIC Frequency Converter Heads offer a choice of input connectors and frequency ranges tor microwave frequency counting up to 40 GHz enough signal reaches the counter to trigger it properly. These conditions dictate using a waveguide instead of a coaxial cable. However, waveguides are suitable only for certain frequency bands, e.g., K-band (1H-213.5 GHz] or R-band (2ti.5-40 GHz), Moreover, they are expensive and lack the mechanical flexibility of the coaxial cable.

Frequency Converter Heads Models 5356AJB/C, Fig. 1. combine the convenience of coaxial cables with the broad frequency bund of a microwave counter [1.5-4(1 GHz), ami can be used for either CW or pulse measurements. These heads convert microwave frequencies to intermediate frequencies [IFI using the sampling technique. The sampli ug frequency input to the head and the IF output from it are connected by a l.fiii-metre cable to the 5:)S5A Automatic Frequency Converter (see article, page 3}. The microwave input frequency to the head is calculated from measurements of the IF and the answer is displayed on the 5345A Counter ((he 5355A is a plug-in for the 5;J45A|, The down-

Table 1

Frequency Ranges and Connectors ot Model 5356A/B.C Frequency Converter Heads

FREQUENCY

HEAD

535tiB Opt. (101 5356G

535fiC Opt, 001

CONNECTOR

Waveguide (WR-42) APC-3.5 Waveguide ! WR-2B)

HEAD CODE

conversion is performed completely in the head and only the IF is connected to the 5355A.

To cover the frequency band up to 40 CI I/., four different connectors are available: N, SMA, APC-3.5 and waveguide. Three models and two options are available In suit various applications. Table 1 shows the frequency ranges of the five heads.

The heads have male connectors because sources generally have female connectors. The 535fiA has an N-tvpe connector and is useful up to 18 GHz. The 53n!iH has an SMA connector, and can be used up to 2(i.!i GHz. To strengthen the SMA male connector, a special collar was designed to protect it. The collar also makes it easier for the customer to connect it to I he source. Some customers prefer using a k-hand waveguide from 1H to 2(5.5 GHz; the 5356B Option 0(11 has a WR-42 connector to meet this need. The input fa 1.5-40 GHz

Frequency Synthesizer Diagram

8B5.2-1056 MHz from 5355A

Fig. 2. Simplified block diagram ot the 5356AB C Frequency Convener Heads

8B5.2-1056 MHz from 5355A

Fig. 2. Simplified block diagram ot the 5356AB C Frequency Convener Heads

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